U.S. patent application number 14/586496 was filed with the patent office on 2015-10-29 for system for evaluating displaying quality of transparent display and method thereof.
This patent application is currently assigned to LG DISPLAY CO., LTD.. The applicant listed for this patent is LG DISPLAY CO., LTD.. Invention is credited to Jaehong KIM, Dongyou LEE, Kyongho LIM, Moojong LIM, Sunhee PARK, Hongseop SHIN.
Application Number | 20150308951 14/586496 |
Document ID | / |
Family ID | 54334512 |
Filed Date | 2015-10-29 |
United States Patent
Application |
20150308951 |
Kind Code |
A1 |
KIM; Jaehong ; et
al. |
October 29, 2015 |
SYSTEM FOR EVALUATING DISPLAYING QUALITY OF TRANSPARENT DISPLAY AND
METHOD THEREOF
Abstract
A system for evaluating a quality of a transparent display, the
system including: a background including any one of a full white
pattern, a full black pattern, and a circle white pattern; a light
detector positioned a first distance away from the background to
measure luminance of the full white pattern, the full black pattern
and the circle white pattern; and a circle transparent pattern
displayed on the transparent display by passing light from at least
one of the full white pattern, the full black pattern and the
circle white pattern, further the transparent display is positioned
between the background and the light detector and at a second
distance away from the light detector, further a purity of the
transparent display is calculated based on luminance of the full
white pattern, the full black pattern, and the circle white pattern
as measured by the light detector through the transparent
display.
Inventors: |
KIM; Jaehong; (Paju-si,
KR) ; LEE; Dongyou; (Seoul, KR) ; LIM;
Moojong; (Seoul, KR) ; LIM; Kyongho; (Paju-si,
KR) ; SHIN; Hongseop; (Paju-si, KR) ; PARK;
Sunhee; (Seoul, KR) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
LG DISPLAY CO., LTD. |
Seoul |
|
KR |
|
|
Assignee: |
LG DISPLAY CO., LTD.
Seoul
KR
|
Family ID: |
54334512 |
Appl. No.: |
14/586496 |
Filed: |
December 30, 2014 |
Current U.S.
Class: |
356/433 |
Current CPC
Class: |
G01N 21/59 20130101;
G01N 21/95 20130101; G01N 2021/9513 20130101 |
International
Class: |
G01N 21/59 20060101
G01N021/59; G02F 1/13 20060101 G02F001/13 |
Foreign Application Data
Date |
Code |
Application Number |
Apr 29, 2014 |
KR |
10-2014-0051467 |
Claims
1. A system for evaluating a quality of a transparent display, the
system comprising: a background including any one of a full white
pattern, a full black pattern, and a circle white pattern; a light
detector positioned a first distance away from the background and
configured to measure luminance of the full white pattern, the full
black pattern and the circle white pattern; and a circle
transparent pattern displayed on the transparent display by passing
light from at least one of the full white pattern, the full black
pattern and the circle white pattern, wherein the transparent
display is positioned between the background and the light detector
and at a position with a second distance away from the light
detector, wherein a purity of the transparent display is calculated
by the following equation 1: Purity ( % ) = L CW - L FK L FW - L FK
.times. 100 ( Equation 1 ) ##EQU00018## and wherein L.sub.FW is a
full white luminance of the full white pattern, L.sub.FK is a full
black luminance of the full black pattern, and L.sub.CW is a circle
white luminance of the circle white pattern as measured by the
light detector through the transparent display, respectively.
2. The system according to claim 1, wherein the first distance is
1.5 m and the second distance is 0.5 m.
3. The system according to claim 1, wherein the circle white
pattern includes a circle pattern having a first diameter and a
full white level, and an ambient surrounding the circle pattern and
having a full black level, and wherein the first diameter
corresponds to a 0.2.degree. height based on a point 1.5 m away
from the light detector.
4. The system according to claim 1, wherein the circle transparent
pattern includes a circle pattern having a maximum white level of
the transparent display and an ambient surrounding the circle
pattern having a maximum black level of the transparent display,
and wherein a second diameter of the circle pattern corresponds to
a 0.2.degree. height based on a point 1.5 m away from the light
detector, and covers an area including at least 500 pixels of the
transparent display.
5. The system according to claim 1, wherein a shape and a size of
the circle white pattern and a receiving lens of the light detector
are the same, and a center of the circle white pattern, a center of
the circle transparent pattern, and a center of the receiving lens
are aligned in a straight line.
6. The system according to claim 1, wherein the background further
represents a circle black pattern, wherein the light detector is
configured to measure a luminance of the circle black pattern
passing through the circle transparent pattern displayed on the
transparent display, and wherein a criteria of the purity is
calculated by the following equation: Criteria = L FW - L CW - L FK
- L CK L FW - L CW .times. 100 .ltoreq. 2 ( % ) ##EQU00019##
wherein L.sub.FW is the full white luminance, L.sub.FK is the full
black luminance, L.sub.CW is the circle white luminance, and
L.sub.CK is the circle black luminance.
7. The system according to claim 6, wherein the circle black
pattern includes a circle pattern with a full black level having a
first diameter and an ambient with a full white level, and wherein
the first diameter corresponds to a 0.2.degree. height based on a
point 1.5 m away from the light detector.
8. The system according to the claim 1, wherein the light detector
is further configured to measure a reference full white luminance
of the full white pattern, a reference full black luminance of the
full black pattern and a reference circle white luminance of the
circle white pattern, without the transparent display being
positioned between the light detector and the background, wherein a
reference purity is calculated by following equation 2: P ref = L
CW , w / o - L FK , w / o L FW , w / o - L FK , w / o ( Equation 2
) ##EQU00020## wherein, L.sub.FW,w/o is the reference full white
luminance, L.sub.FK,w/o is the reference full black luminance, and
L.sub.CW,w/o is the reference circle white luminance, and wherein
the purity calculated by the equation 1 is decided as a measured
purity, wherein a new purity of the transparent display is
calculated by the following equation 3: P ref = L CW , w / o - L FK
, w / o L FW , w / o - L FK , w / o ( Equation 2 ) ##EQU00021##
wherein P.sub.exp is the measured purity, and P.sub.ref is the
reference purity.
9. A method for evaluating a quality of a transparent display, the
method comprising: positioning a background configured to represent
any one of a full white pattern, a full black pattern, and a circle
white pattern at a first distance away from a light detector;
aligning a center of the circle white pattern and a center of a
receiving lens of the light detector onto an alignment axis;
positioning the transparent display between the background and the
light detector and at a position with a second distance away from
the light detector; displaying a circle transparent pattern on a
center of the transparent display; aligning a center of the circle
transparent pattern onto the alignment axis; measuring a full white
luminance of the full white pattern, a full black luminance of the
full black pattern and a circle white luminance of the circle white
pattern represented on the background, through the transparent
display, with the light detector; and calculating a purity of the
transparent display using the following equation 1: Purity ( % ) =
L CW - L FK L FW - L FK .times. 100 ( Equation 1 ) ##EQU00022##
wherein, L.sub.FW is the full white luminance, L.sub.FK is the full
black luminance, and L.sub.CW is the circle white luminance.
10. The method according to claim 9, wherein the first distance is
1.5 m and the second distance is 0.5 m.
11. The method according to claim 9, wherein the circle white
pattern includes a circle pattern having a first diameter and a
full white level, and an ambient surrounding the circle pattern and
having a full black level, and wherein the first diameter
corresponds to a 0.2.degree. height based on a point 1.5 m away
from the light detector.
12. The method according to claim 9, wherein the circle transparent
pattern includes a circle pattern having a maximum white level of
the transparent display and an ambient surrounding the circle
pattern having a maximum black level of the transparent display,
and wherein a second diameter of the circle pattern corresponds to
a 0.2.degree. height based on a point 1.5 m away from the light
detector and covers an area including at least 500 pixels of the
transparent display.
13. The method according to claim 9, wherein a shape and a size of
the circle white pattern and a receiving lens of the light detector
are the same, and a center of the circle white pattern, a center of
the circle transparent pattern, and a center of the receiving lens
are aligned in a straight line.
14. The method according to claim 9, wherein the background is
further configured to represent a circle black pattern, and wherein
the method further comprises: measuring a circle black luminance of
the circle black pattern passing through the circle transparent
pattern displayed on the transparent display; calculating a
criteria of the purity using the circle black luminance of the
circle black pattern measured by the light detector; and evaluating
an allowance error in which the calculated purity is decided as the
purity of the transparent display when a criteria is satisfied; and
repeating the aligning of the alignment axis when the criteria is
not satisfied, wherein the criteria is calculated by the following
equation: Criteria = L FW - L CW - L FK - L CK L FW - L CW .times.
100 .ltoreq. 2 ( % ) ##EQU00023## wherein L.sub.FW is the full
white luminance, L.sub.FK is the full black luminance, L.sub.CW is
the circle white luminance, and L.sub.CK is the circle black
luminance.
15. The method according to claim 14, wherein the circle black
pattern includes a circle pattern with a full black level having a
first diameter and an ambient with a full white level, and wherein
the first diameter corresponds to a 0.2.degree. height based on a
point 1.5 m away from the light detector.
16. The method according to claim 9, wherein between the
positioning of the background and the positioning of the
transparent display, the method further comprises measuring a
reference full white luminance of the full white pattern, a
reference full black luminance of the full black pattern and a
reference circle white luminance of the circle white pattern, by
the light detector without the transparent display being positioned
between the light detector and the background; and calculating a
reference purity of the background by the following equation 2: P
ref = L CW , w / o - L FK , w / o L FW , w / o - L FK , w / o (
Equation 2 ) ##EQU00024## wherein L.sub.FW,w/o is the reference
full white luminance, L.sub.FK,w/o is the reference full black
luminance, and L.sub.CW,w/o is the reference circle white
luminance, wherein the purity calculated by the equation 1 is
decided as a measured purity, and wherein a new purity of the
transparent display is calculated by the following equation 3:
Purity ( % ) = P exp P ref .times. 100 ( Equation 3 ) ##EQU00025##
wherein P.sub.exp is the measured purity, and P.sub.ref is the
reference purity.
Description
[0001] This application claims the benefit of Korea Patent
Application No. 10-2014-0051467 filed in the Republic of Korea on
Apr. 29, 2014, which is incorporated herein by reference for all
purposes as if fully set forth herein.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention relates to a system for evaluating the
display quality of a transparent display and method thereof.
Particularly, the present invention provides a new standard (or,
index, measure, scale) and a system for evaluating how well a
transparent display presents display information with the
background view (e.g., the scene behind the display/objects viewed
through the display) through the display at the same time.
[0004] 2. Discussion of the Related Art
[0005] Various flat panel display devices providing video
information including still pictures, moving pictures and/or
animations are developed for overcoming many drawbacks of the
cathode ray tube such as its heavy weight and bulk volume. Flat
panel display devices include the liquid crystal display device
(LCD), the field emission display (FED), the plasma display panel
(PDP) and the electroluminance device (EL).
[0006] The liquid crystal display and the organic light emitting
diode display are representative of flat displays that are widely
applied in various appliances including portable devices and/or
television sets. However, these flat panel displays are developed
just for a display system, but they are not applied to various
applications. For example, a transparent display displays video
information on its screen when the display is activated and the
user can see objects behind the display through the display panel
when it is not activated. However, the standard for evaluating the
quality of a transparent display is not clear and it is very hard
for a user and/or consumer to decide which display is suitable for
his or her displaying environment and/or purpose.
[0007] In more detail, the transparent display is like see through
glass when it is not operated, and presents video information when
it is operated. In some instances, when it is activated, the user
sees only the video information presented by the transparent
display. In other instances, even when the transparent display is
operated, the user may see the video information and the background
scene behind the display panel through the display panel (e.g., a
view of the objects behind the display). For example, a heads up
display (HUD) is a typical example of such a transparent display.
Until now, such a transparent display is only used in environments
in which a very expensive display system is applied without regard
to the price in the market. However, the requirement of a
transparent display in various fields including advertising
displays and home appliances is increasing.
[0008] FIG. 1 is a perspective diagram illustrating the structure
of a transparent display using a liquid crystal display. The
transparent liquid crystal display includes a liquid crystal
display panel LCDP, a light guide LG and a light source. The liquid
crystal display panel LCDP includes two polarization sheets and a
liquid crystal panel LCP inserted between the two polarization
sheets. The liquid crystal panel LCP includes an upper substrate
SU, a lower substrate SL and a liquid crystal layer LC inserted
between the two substrates SU and SL.
[0009] At the upper side and the lower side of the liquid crystal
panel LCP, an upper polarization sheet PU and a lower polarization
sheet PL are disposed, respectively. On the inner surfaces of the
upper substrate SU and the lower substrate SL, a plurality of lines
and black matrixes are disposed as defining a plurality of pixel
areas arranged in a matrix manner, and the common electrode and the
pixel electrode for driving the liquid crystal layer LC. Further, a
color filter for representing a full color picture is included. The
upper polarization sheet PU is disposed on the outer surface of the
upper substrate SU, and the lower polarization sheet PL is disposed
on the outer surface of the lower substrate SL.
[0010] Generally, the light axis of the upper polarization sheet PU
is perpendicular to the light axis of the lower polarization sheet
PL so that a real black level can be reproduced exactly. However,
for a transparent display, if the upper polarization sheet PU and
the lower polarization sheet PL are disposed like they are in a
common liquid crystal display, when it is not activated, light
cannot pass through the liquid crystal display panel LCDP. The
situation in which the light axis of the upper polarization sheet
PU is perpendicular to that of the lower polarization sheet PL is
referred to as the `Normally Black (or NB) mode,` because it
represents the black level under normal conditions (e.g., while not
operating).
[0011] For a transparent display, the display can be in a
transparent state when the liquid crystal display panel LCDP is not
activated. Therefore, it is preferable that the liquid crystal
display panel LCDP for the transparent display be made in the
`Normally White (or NW) mode` which represents the white level
under normal conditions. Unlike the normally black mode, the
normally white mode cannot be acquired by the parallel arrangement
of the light axes of the upper polarization sheet PU and the lower
polarization sheet PL. The polarization characteristics of the
liquid crystal layer LC used for the liquid crystal panel LCP
should be considered.
[0012] For the vertical electric field type of liquid crystal
display using a twisted nematic mode liquid crystal layer, even
though the light axes of the upper polarization sheet PU and the
lower polarization sheet PL are perpendicular, the normally white
mode can be acquired. On the contrary, for the horizontal electric
field type of liquid crystal display, the normally white mode can
be established with the light axes of the upper polarization sheet
PU and the lower polarization sheet PL being perpendicular.
[0013] Under the liquid crystal display panel LCDP, the light guide
LG and the light source LS are disposed. The light source LS is
disposed at one side surface of the light guide LG to provide light
to the light guide LG. The light guide LG diffuses light from the
light source LS throughout the whole inner space of the light guide
LG, and refracts light to the upper surface facing the liquid
crystal display panel LCDP. To do this, a reflective pattern is
disposed on the rear surface (or, bottom surface) of the light
guide LG. Since the light guide LG should ensure a transparent
condition, the reflective pattern would be one of the prism
pattern, the lenticular lens pattern or the micro lens pattern.
[0014] As mentioned above, when the transparent display is not
activated, it is in a transparent condition like clear glass. On
the contrary, when electric power is supplied for using it as a
display device, it can provide video information together with the
scene behind the display (e.g., objects behind the display remain
viewable). Further, the transparent display should include a back
light unit that ensures the transparent property, in contrast to a
normal liquid crystal display. Therefore, the optical sheets used
in normal liquid crystal displays for enhancing the brightness of
the back light should not be used for a transparent display.
[0015] Hereinafter, referring to FIGS. 2 and 3, a related art
transparent display using the organic light emitting diode display
will be explained. In particular, FIG. 2 is a plane view
illustrating the structure of a transparent organic light emitting
diode display, and FIG. 3 is a cross sectional view illustrating
the structure of the bottom emission type of transparent organic
light emitting diode display along the cutting line I-I' of FIG. 2.
The bottom emission type of transparent organic light emitting
diode display according to the related art includes a switching
thin film transistor ST, a driving thin film transistor DT
connected to the switching thin film transistor ST, and an organic
light emitting diode OLE connected to the driving thin film
transistor DT.
[0016] One pixel area of the transparent organic light emitting
diode display includes a light emitting area LEA for representing
the video information and a transparent area TRA for penetrating or
transmitting/communicating the background scene. For example, the
pixel area is defined by a scan line SL, a data line DL and a
driving current line VDD, and the pixel area is divided into the
light emitting area LEA and the transparent area TRA. Further, the
pixel area includes a non-light emitting area where any light for
representing video information and from the background scene are
not suggested.
[0017] The switching thin film transistor ST is formed where the
scan line SL and the data line DL cross each other. The switching
thin film transistor ST acts for selecting the pixel connected to
the switching thin film transistor ST. The switching thin film
transistor ST includes a gate electrode SG branching from the scan
line SL, a semiconductor channel layer SA overlapping with the gate
electrode SG, a source electrode SS and a drain electrode SD. The
driving thin film transistor DT drives an anode electrode ANO of
the organic light emitting diode OLE disposed at the pixel selected
by the switching thin film transistor ST. The driving thin film
transistor DT includes a gate electrode DG connected to the drain
electrode SD of the switching thin film transistor ST, a
semiconductor channel layer DA, a source electrode DS connected to
the driving current line VDD, and a drain electrode DD.
[0018] The drain electrode DD of the driving thin film transistor
DT is connected to the anode electrode ANO of the organic light
emitting diode OLE. The organic light emitting layer OL is inserted
between the anode electrode ANO and the cathode electrode CAT.
Further, the cathode electrode CAT is connected to the base voltage
(or, ground voltage) VSS. A storage capacitance Cst is disposed
between the gate electrode DG of the driving thin film transistor
DT and the driving current line VDD or between the gate electrode
DG of the driving thin film transistor DT and the drain electrode
DD of the driving thin film transistor DT.
[0019] In the view of the cross sectional structure shown in FIG.
3, the gate electrodes SG and DG of the switching thin film
transistor ST and the driving thin film transistor DT are formed on
the substrate SUB of the transparent organic light emitting diode
display. On the gate electrodes SG and DG, the gate insulator GI is
deposited. On the gate insulator GI overlapping with the gate
electrodes SG and DG, the semiconductor layers SA and DA are
formed, respectively. Further, on the semiconductor layer SA and
DA, the source electrode SS and DS and the drain electrode SD and
DD facing and separated from each other are formed. The drain
electrode SD of the switching thin film transistor ST is connected
to the gate electrode DG of the driving thin film transistor DT via
the drain contact hole DH penetrating the gate insulator GI. In
addition, the passivation layer PAS is deposited on the substrate
SUB having the switching thin film transistor ST and the driving
thin film transistor DT.
[0020] In some instances, a color filter CF is further disposed on
the passivation layer PAS. In these instances, it is preferable
that the color filter CF be formed within the light emitting area
LEA. For example, the color filter CF can be formed where the anode
electrode ANO would be formed later. For representing full color,
the color filter CF may include any one of a red pigment, a green
pigment and a blue pigment. The color filter CF set including the
red color filter R, the green color filter G and the blue color
filter B is arrayed in a matrix manner.
[0021] As mentioned above, the substrate SUB having the thin film
transistors ST and DT has an uneven surface and level differences
because there are many elements. It is preferable for the organic
light emitting layer OL to be formed on an even surface to ensure
uniform light emission distribution over all of the area of the
organic light emitting layer OL. Therefore, in order to make the
surface of the substrate SUB smooth, the over coat layer OC (or,
the planar layer) is deposited over the substrate SUB.
[0022] On the over coat layer OC, an anode electrode ANO of the
organic light emitting diode OLE is formed. Here, the anode
electrode ANO is connected to the drain electrode DD of the driving
thin film transistor DT via the contact hole formed at the over
coat layer OC and the passivation layer PAS. It is preferable that
the anode electrode ANO is formed within the light emitting area
LEA. The ratio of the light emitting area LEA and the transparent
area TRA is not strictly defined. That is, it can be selected among
the various ratio values according to the specification for the
brightness of the display and purpose of the display.
[0023] In the bottom emission type of organic light emitting diode
display representing full color, the anode electrode includes a
transparent conductive material such as an indium tin oxide (or,
ITO) or an indium zinc oxide (or, IZO). A bank BN is formed on the
substrate SUB having the anode electrode ANO. It is preferable that
the bank BN separates the light emitting area LEA and the
transparent area TRA and has apertures exposing each area,
respectively. If required, the bank BN can have one aperture
exposing the light emitting area LEA and the transparent area TRA.
Otherwise, the bank BN has a pattern for exposing the light
emitting area LEA but not exposing the transparent area TRA. The
exposed portion of the anode electrode ANO by the bank BN would be
the actual light emitting area.
[0024] On the surface of the substrate SUB where the anode
electrode ANO of the light emitting area LEA is exposed from the
bank BN, the organic light emitting layer OL is formed. For the
bottom emission type in which the color filter CF is disposed under
the anode electrode ANO, the organic light emitting layer OL may
include an organic material which can generate white color. On the
organic light emitting layer OL, the cathode electrode CAT is
formed. Consequently, the organic light emitting diode OLE
including the anode electrode ANO, the organic light emitting layer
OL and the cathode electrode CAT and driven by the driving thin
film transistor DT is formed.
[0025] A transparent display having the structure mentioned above
appears as transparent glass when it is not activated so that the
background scene can be seen by a user located in front of the
display. When the user turns on the display, the user can see the
video information with the background scene or without the
background scene. This can be applied to various applications.
[0026] The transparent display should have a good property for
displaying high quality video information and for providing high
visual quality of the background scene passing through the display
panel. However, the standard (or, index, measure, scale or
barometer) for evaluating the visual quality and/or property of a
transparent display is not clearly defined in the field market.
Until now, the quality of a transparent display has been evaluated
by adopting the measurement standards for transparent substrates
such as bare glass. For example, the standard for evaluating a
transparent substrate according to the related art is measurement
of the haze or the clarity.
[0027] The haze means the diffusing degrees of the light is defined
by the percent of transmitted light that is scattered so that its
direction deviates more than a specified angle from the direction
of the incident beam (ASTM D 1003). In this test method, the
specified angle is 2.5.degree. (0.044 rad). FIG. 4 is a schematic
diagram illustrating the method for measuring the haze according to
the related art. The light IL radiated from the light source LS
enters into the measuring instrument HMD via the entrance ETR after
passing through the transparent display TS. Here, the light TL
passing through the transparent display TS is scattered. The haze
measuring instrument HMD can measure the light out of the exit EXT,
where the measured light is within the specified angle)(2.5.degree.
about the light incident axis. Using the instrument as shown in
FIG. 4, the total amount of the light, T.sub.t, passing through the
transparent display TS and measured at the entrance ETR and the
partial amount of the light, T.sub.d, propagating within the
specified angle)(2.5.degree. at the exit EXT are measured,
respectively. And then, the haze is calculated by the following
Equation 1.
Haze = T d Tt .times. 100 ( % ) ( Equation 1 ) ##EQU00001##
[0028] The clarity is defined as the ability to transmit
image-forming light, in correlation with its regular transmittance
(ASTM D 1746-03), and can be acquired as measuring the ratio of the
amount of light passing within the specific angle 2.5.degree. to
the whole amount of light transmitted through the ring pattern with
the contrast modulation. FIG. 5 is a schematic diagram illustrating
the related art method for measuring the clarity. The light IL is
radiated from the light source LS. The radiated light TL is
measured using the clarity measuring instrument CMD. Disposing a
ring pattern CP at the exit EXT of the clarity measuring instrument
CMD, and measuring the amount of the light, the clarity can be
calculated. As shown in FIG. 5, the light amount, I.sub.R, passing
through the ring pattern RS and the light amount, I.sub.c, passing
through the center circle pattern CS are measured and then the
clarity is calculated by the following Equation 2.
Clarity = I C - I R I C + I R .times. 100 ( % ) ( Equation 2 )
##EQU00002##
[0029] However, these values cannot accurately evaluate the quality
of a transparent display exactly. For example, a transparent
display having a high value of the haze or the clarity has a worse
quality than a transparent display having a lower value of the haze
or the clarity.
[0030] As mentioned above, at least on one surface of the
transparent display (for ensuring the transparent property),
various elements configuring the pixel are formed, even though they
are not easily seen. Therefore, when light from the background
scene passes through the transparent display panel, the light has
various optical effects due to the different elements. For example,
the incident light from the rear surface of the transparent display
may be refracted, reflected and/or absorbed as the light passes
through the transparent display panel. Further, because the various
elements have tiny patterns, these patterns act as silts so that
various optical phenomena such as diffraction and/or scattering
occur.
[0031] Unlike a transparent liquid crystal display, a transparent
organic light emitting diode display has no transparent electrode
in the transparent area TRA so that the background light may not be
diffracted and/or refracted by the elements. As a result, it has a
better transparent quality than a liquid crystal display. However,
there are lines disposed between the transparent areas TRA.
Especially, for a high resolution transparent organic light
emitting diode display, the background light may be easily
diffracted and/or refracted by the display elements so that the
transparent quality is degraded.
[0032] The haze and the clarity are the evaluation standards for
bare glass. Therefore, they are not suitable for evaluating the
transparent property of a transparent display panel in which
various transparent elements are disposed thereon. Consequently,
any related standard cannot evaluate the quality of a transparent
display exactly or correctly, and there is no method for evaluating
the transparent display quality.
SUMMARY OF THE INVENTION
[0033] In order to overcome the above mentioned drawbacks, one
object purpose of the present invention is to provide a system for
evaluating the quality of a transparent display and a method for
measuring the quality of a transparent display.
[0034] Another object of the present invention is to provide a
novel standard in which the measured property is proportional to
the actual quality of a transparent display evaluated by the
user.
[0035] Still another object of the present invention is to provide
a system for measuring the new standard for evaluating the quality
of a transparent display, and a method for measuring the same.
[0036] In order to accomplish the above objects, embodiments of the
present invention provide a system for evaluating a quality of a
transparent display including: a background representing any one of
a full white pattern, a full black pattern, and a circle white
pattern; a light detector disposed with a first distance apart from
the background for measuring luminance of the full white pattern,
the full black pattern and the circle white pattern; and a circle
transparent pattern displayed on the transparent display passing
lights from at least one of the full white pattern, the full black
pattern and the circle white patter, wherein the transparent
display is placed between the background and the light detector and
at a position with a second distance apart from the light detector,
wherein a purity of the transparent display is calculated by the
following equation 1 with a full white luminance of the full white
pattern, a full black luminance of the full black pattern and a
circle white luminance of the circle white pattern which are
measured by the light detector through the transparent display.
Purity ( % ) = L CW - L FK L FW - L FK .times. 100 ( Equation 1 )
##EQU00003##
[0037] Here, L.sub.FW is the full white luminance, L.sub.FK is the
full black luminance, and L.sub.CW is the circle white
luminance.
[0038] In one embodiment, the first distance is 1.5 m and the
second distance is 0.5 m.
[0039] In one embodiment, the circle white pattern includes a
circle pattern having a first diameter and a full white level, and
an ambient surrounding the circle pattern and having a full black
level, and wherein the first diameter corresponds to a 0.2.degree.
height based on a point 1.5 m apart.
[0040] In one embodiment, the circle transparent pattern includes a
circle pattern having a maximum white level of the transparent
display and an ambient surrounding the circle pattern having a
maximum black level of the transparent display, and wherein the
second diameter is selected as one condition in which the second
diameter corresponds to a 0.2.degree. height based on a point 1.5 m
apart, and that the second diameter covers an area including at
least 500 pixels of the transparent display.
[0041] In one embodiment, the circle white pattern has a shape and
a size the same as a receiving lens of the light detector, and a
center of the circle white pattern, a center of the circle
transparent pattern, and a center of the receiving lens are aligned
onto a straight line.
[0042] In one embodiment, the background further represents a
circle black pattern, the light detector further measures a
luminance of the circle black pattern passing through the circle
transparent pattern displayed on the transparent display, wherein a
criteria of the purity is calculated by the following equation with
the circle black luminance of the circle black pattern is measured
by the light detector.
Criteria = | L FW - L CW | - | L FK - L CK | | L FW - L CW |
.times. 100 .ltoreq. 2 ( % ) ##EQU00004##
[0043] Here, L.sub.FW is the full white luminance, L.sub.FK is the
full black luminance, L.sub.CW is the circle white luminance, and
L.sub.CK is the circle black luminance.
[0044] In one embodiment, the circle black pattern includes a
circle pattern of full black level having a first diameter and an
ambient of full white level, and the first diameter is
corresponding to a 0.2.degree. height based on a point 1.5 m
apart.
[0045] In one embodiment, the light detector further measures a
reference full white luminance of the full white pattern, a
reference full black luminance of the full black pattern and a
reference circle white luminance of the circle white pattern,
without the transparent display, a reference purity is calculated
by the following equation 2,
P ref = L CW , w / o - L FK , w / o L FW , w / o - L FK , w / o (
Equation 2 ) ##EQU00005##
[0046] here, L.sub.FW,w/o is the reference full white luminance,
L.sub.FK,w/o is the reference full black luminance, and
L.sub.CW,w/o is the reference circle white luminance.
[0047] The purity calculated by equation 1 is decided as a measured
purity, and a new purity of the transparent display is calculated
by the following equation 3 with the reference purity and the
measured purity.
Purity ( % ) = P exp P ref .times. 100 ( Equation 3 )
##EQU00006##
[0048] Here, P.sub.exp is the measured purity, and P.sub.ref is the
reference purity.
[0049] Further, the present invention can provide a method for
evaluating a quality of a transparent display comprising:
displacing a background configured to represent any one of a full
white pattern, a full black pattern, and a circle white pattern and
a light detector with a first distance apart from the background,
and aligning a center of the circle white pattern and a center of a
receiving lens of the light detector onto an alignment axis;
placing the transparent display between the background and the
light detector and at a position with a second distance apart from
the light detector; displaying a circle transparent pattern on a
center of the transparent display, and aligning a center of the
circle transparent pattern onto the alignment axis; measuring
luminance of the full white pattern, the full black pattern and the
circle white pattern represented on the background, through the
transparent display; and calculating a purity of the transparent
display based on a full white luminance of the full white pattern,
a full black luminance of the full black pattern and a circle white
luminance of the circle white pattern, wherein the purity is
calculated by the following equation 1.
Purity ( % ) = L CW - L FK L FW - L FK .times. 100 ( Equation 1 )
##EQU00007##
[0050] Here, L.sub.FW is the full white luminance, L.sub.FK is the
full black luminance, and L.sub.CW is the circle white
luminance.
[0051] In one embodiment, the first distance is 1.5 m and the
second distance is 0.5 m.
[0052] In one embodiment, the circle white pattern includes a
circle pattern having a first diameter and a full white level, and
an ambient surrounding the circle pattern and having a full black
level, the first diameter corresponds to a 0.2.degree. height based
on a point 1.5 m apart, the circle transparent pattern includes a
circle pattern having a maximum white level of the transparent
display and an ambient surrounding the circle pattern having a
maximum black level of the transparent display, and the second
diameter is selected as one condition being that the second
diameter corresponds to a 0.2.degree. height based on a point 1.5 m
apart, and that the second diameter covers an area including at
least 500 pixels of the transparent display.
[0053] In one embodiment, when measuring luminance, the background
further represents a circle black pattern, the light detector
further measures a luminance of the circle black pattern passing
through the circle transparent pattern displayed on the transparent
display; and further comprising: calculating a criteria of the
purity with the circle black luminance of the circle black pattern
measured by the light detector; and evaluating an allowance error
in which the calculated purity is decided as the purity of the
transparent display when the criteria is satisfied, and the
aligning the alignment axis is repeated when the criteria is not
satisfied, the criteria is calculated by following equation.
Criteria = | L FW - L CW | - | L FK - L CK | | L FW - L CW |
.times. 100 .ltoreq. 2 ( % ) ##EQU00008##
[0054] Here, L.sub.FW id the full white luminance, L.sub.FK id the
full black luminance, L.sub.CW id the circle white luminance, and
L.sub.CK id the circle black luminance.
[0055] In one embodiment, between the displacing the background and
the light detector and the placing the transparent display, further
comprising: measuring reference full white luminance of the full
white pattern, a reference full black luminance of the full black
pattern and a reference circle white luminance of the circle white
pattern, without the transparent display; and calculating a
reference purity of the background by equation 2.
P ref = L CW , w / o - L FK , w / o L FW , w / o - L FK , w / o (
Equation 2 ) ##EQU00009##
[0056] Here, L.sub.FW,w/o is the reference full white luminance,
L.sub.FW,w/o is the reference full black luminance, and
L.sub.CW,w/o is the reference circle white luminance.
[0057] The purity calculated by equation 1 is decided as a measured
purity, and a new purity of the transparent display is calculated
by the following equation 3.
Purity ( % ) = P exp P ref .times. 100 ( Equation 3 )
##EQU00010##
[0058] Here, P.sub.exp is the measured purity, and P.sub.ref is the
reference purity.
[0059] The present invention can provide a new standard for
evaluating a quality of a transparent display, the purity,
considering the amount of the diffracted and scattered lights by
transparent electrodes formed in the transparent display. According
to the present invention, the purity is a new standard for
evaluating the quality of a transparent display that is exactly
proportional to the degree of the transparent property for the
scene viewed by the observer through the transparent display. The
purity is a new standard evaluating the quality of the transparent
display which exactly defines how the background scene is seen by
the observer through the transparent display. Further, the present
invention can provide a system for evaluating the purity of a
transparent display and a method for evaluating the purity.
According to the present invention, unlike the haze and the clarity
evaluation methods, the degree in which the background scene is
affected by the transparent display can be accurately
evaluated.
BRIEF DESCRIPTION OF THE DRAWINGS
[0060] The accompanying drawings, which are included to provide a
further understanding of the invention and are incorporated in and
constitute a part of this specification, illustrate embodiments of
the invention and together with the description serve to explain
the principles of the invention.
[0061] In the drawings:
[0062] FIG. 1 is a perspective diagram illustrating the structure
of a transparent display using a liquid crystal display.
[0063] FIG. 2 is a plane view illustrating the structure of a
transparent organic light emitting diode display.
[0064] FIG. 3 is a cross sectional view illustrating the structure
of a bottom emission type of transparent organic light emitting
diode display along the cutting line I-I' of FIG. 2.
[0065] FIG. 4 is a schematic diagram illustrating the method for
measuring the haze of a transparent display according to the
related art.
[0066] FIG. 5 is a schematic diagram illustrating the method for
measuring the clarity of a transparent display according to the
related art.
[0067] FIG. 6 is a schematic diagram illustrating a system for
measuring the purity, the new standard for evaluating the quality
of a transparent display, according to an embodiment of the present
invention.
[0068] FIG. 7 is a diagram illustrating the luminescence of the
representative patterns in a system for measuring the purity
according to an embodiment of the present invention.
[0069] FIG. 8 is a flow chart illustrating a method for measuring
the purity, which is a new standard for evaluating the quality of a
transparent display, according to an embodiment of the present
invention.
[0070] FIG. 9 is a flow chart illustrating a method for measuring
the purity, which is a new standard for evaluating the quality of a
transparent display, according to an embodiment of the present
invention.
[0071] FIG. 10 is a perspective view illustrating a system for
measuring the purity according to an embodiment of the present
invention.
DETAILED DESCRIPTION
[0072] Referring to the attached figures, embodiments of the
present invention will be explained. Like reference numerals
designate like elements throughout the detailed description.
However, the present invention is not restricted by these
embodiments but can be applied to various changes or modifications
without changing the technical spirit. In the following
embodiments, the names of the elements are selected by considering
the easiness for explanation so that they may be different from
their actual names.
[0073] The present invention provides a new standard, the purity,
for evaluating the quality of a transparent display. The
descriptive definition of the purity can be defined as the degree
of accuracy by which the observer and/or user can view the combined
images at the permeate side of a transparent display.
[0074] To convert the descriptive definition into an objective
numerical value, a mathematical definition of the purity is used.
The mathematical definition of the purity can be viewed as a ratio
of the luminance (or, brightness) changed by the diffraction and
scattering to the maximum luminance passing though the transparent
display by considering the black luminance of the background. This
is defined as the following Equation 3.
Purity ( % ) = L ( Brightness ) pattern - passing L ( Brightness )
total - passing .times. 100 ( Equation 3 ) ##EQU00011##
[0075] Here, the `L(Brightness).sub.total-passing` is the maximum
brightness of the background passing through the transparent
display considering the black luminance of the background. It also
can be referred to as the reference luminance or the reference
brightness. Further, the `L(Brightness).sub.pattern-passing` is the
amount of luminance changed by the diffraction and/or scattering
affections. It also means the `changed luminance` by the
diffraction and scattering of the light passing through a minimum
pattern.
[0076] How the `reference luminance` and the `changed luminance`
are measured, as in the above Equation 3, will be described
referring to FIG. 6, which illustrates a method and a system for
measuring the purity, the new standard for evaluating the quality
of a transparent display will be explained. In particular, FIG. 6
is a schematic diagram illustrating a system for measuring the
purity, the new standard for evaluating the quality of a
transparent display, according to an embodiment of the present
invention.
[0077] Referring to FIG. 6, the distance between a background BG
and an observer is set to 1.5 m, as the standard distance in the
optical measurement method. At the observer's position, a luminance
detector LMD is located. A transparent display TS is disposed
between the transparent display TS and the luminance detector LMD.
The transparent display TS is located 0.5 m away from the luminance
detector LMD. These location settings are decided by considering a
representative environment for applying the transparent display by
which an observer would view the scene of the background BG and the
image represented on the transparent display, and by considering
the general and standard conditions used when measuring the optical
characteristics.
[0078] At the background BG, any one of a full white pattern FW, a
circle white pattern CW, a circle black pattern CK and a full black
pattern FK are selectively positioned. Here, the circle white
pattern CW is a pattern in which one small circle having a pure
white level is formed in the center of the background having a pure
black level. Further, the circle black pattern CK is a pattern in
which one small circle having a pure black level is formed in the
center of the background having a pure white level.
[0079] The sizes of the circle white pattern CW and the circle
black pattern CK correspond to the 0.2.degree. height based on the
center of the receiving lens AP of the light detector LMD spaced
1.5 m away from the patterns. Further, it is preferable that these
patterns have the same shape and the same size as the aperture of
the receiving lens AP. These conditions are decided by considering
that the interference and affection of the light going into the
light detector LMD from the circle patterns by the ambient light is
minimized.
[0080] The size of 0.2.degree. of the circle patterns is selected
by considering that the minimum required height is 0.21.degree. in
which a person can exactly recognize a character or symbol from a
distance of 1.5 m. Preferably, the size of the circle patterns and
the aperture of the receiving lens AP of the light detector LMD are
about 12.5 mm in diameter.
[0081] Further, a circle transparent pattern CTP is represented on
the transparent display TS disposed between the background BG and
the light detector LMD. The circle transparent pattern CTP having a
maximum white level is positioned in the center of the background
having a maximum black level of the transparent display. It is
preferable that the center point of the circle transparent pattern
CTP be aligned with the center point of the circle white pattern CW
or the circle black pattern CK and the center point of the
receiving lens AP of the light detector LMD.
[0082] In addition, the circle transparent pattern CTP preferably
has a diameter corresponding to a height of 1.degree. from the
point 1.5 m distance. Here, the height 1.degree. is selected as the
circle area of the circle transparent pattern CTP that includes
about 500 pixels. Therefore, the diameter of the circle transparent
pattern CTP is not required to be just 1.degree.. Rather, it would
be satisfactory as long as at least 500 pixels are included in the
area of the circle transparent pattern CTP and that the size of the
circle transparent pattern CTP is larger than the sizes of the
circle white pattern CW and the circle black pattern CK. In order
to minimize interference by the ambient area surrounding the circle
transparent pattern CTP, it is preferable that the background
surrounding the circle transparent patter CTP have the maximum
black level that can be represented by the transparent display.
[0083] The present invention relates to a system for evaluating how
well the background scene BG passing through the transparent
display TS can be recognized by the observer. Therefore, it is
preferable that interference by ambient light should be minimized
when measuring the purity. Preferably, the entire size of the
background BG be much larger than the size of the transparent
display TS. It is not required that a specific rational
relationship between the size of the background BG and the size of
the transparent display TS be defined. However, it is preferable
that the size of the background BG is at least twice of the size of
the transparent display TS.
[0084] With the system shown in FIG. 6, the full white pattern FW
is represented on the background BG, and the luminance (or
brightness) is measured by the light detector LMD. This value is
set as the full white luminance L.sub.FW. Then, the full black
pattern FK is represented on the background BG and the luminance is
measured by the light detector LMD. This value is set as the full
black luminance L.sub.FK. Next, the circle white pattern CW is
disposed at the background BG, and the luminance is measured by the
light detector LIVID. This value is set as the circle white
luminance L.sub.CW. Lastly, the circle black pattern CK is
positioned at the background BG, and the luminance is measured by
the light detector LIVID. This value is set as the circle black
luminance L.sub.CK. Theses measured luminances are made up as shown
in FIG. 7. In particular, FIG. 7 is a diagram illustrating the
luminance of the representative patterns in a system for measuring
the purity according to an embodiment of the present invention.
[0085] Referring to FIG. 7, the `reference luminance L.sub.ref` is
the difference between the `full white luminance L.sub.FW` and the
`full black luminance L.sub.FK`, that is, L.sub.FW-L.sub.FK. Based
on the `reference luminance`, the difference between the `circle
white luminance L.sub.CW` and the `full black luminance L.sub.FK`
is the `changed luminance L.sub.aperture,CK of the circle black
pattern CK` by the diffraction and scattering. In addition, the
difference between the `full white luminance L.sub.FW` and the
`circle black luminance L.sub.CK` is the `changed luminance
L.sub.aperture,CW of the circle white pattern CW` by the
diffraction and scattering.
[0086] Using these four luminance values with Equation 3, the
purity can be defined using the following Equation 4.
Purity ( % ) = L aperture L ref .times. 100 = L CW - L FK L FW - L
FK .times. 100 ( Equation 4 ) ##EQU00012##
[0087] Here, the L.sub.CW is the circle white luminance, the
L.sub.FK means the full black luminance, and the L.sub.FW means the
full white luminance.
[0088] As for another expression, the purity can be defined using
the following Equation 5.
Purity ( % ) = ( 1 - .DELTA. L W L ref ) .times. 100 = ( 1 - L FW -
L CW L FW - L FK ) .times. 100 ( Equation 5 ) ##EQU00013##
[0089] Here, .DELTA.L.sub.W is the amount of luminance distorted by
the diffraction and the scattering, as the difference (absolute
value) between the full white luminance L.sub.FW and the circle
white luminance L.sub.CW. In addition, L.sub.CW is the circle white
luminance, L.sub.FK is the full black luminance, and L.sub.FW is
the full white luminance.
[0090] The difference between the `full white luminance L.sub.FW`
and the `circle white luminance L.sub.CW`, as the distorted
luminance of the light from the circle white pattern CW by the
transparent display, can be defined as .DELTA.L.sub.W. The
difference (absolute value) between the `full black luminance
L.sub.FK` and the `circle black luminance L.sub.CK`, as the
distorted luminance of the light from the circle black pattern CK
by the transparent display, can be defined as .DELTA.L.sub.K. Here,
as for the same transparent display, this distorted luminance
should be the same value. That is, ideally, .DELTA.L.sub.W should
be same with .DELTA.L.sub.K.
[0091] To make .DELTA.L.sub.W to be the same as .DELTA.L.sub.K, the
centers of the circle patterns in the background BG should be
exactly aligned with the center of the receiving lens AP of the
light detector LMD. Actually, in the system and the method
explained in the FIG. 6, with the four measured luminances, when
the difference between .DELTA.L.sub.W and .DELTA.L.sub.K is less
than 2% tolerance, then the measurement for the purity is correctly
performed. That is, the measured values are reliable.
[0092] In other words, when the following Equation 6 is satisfied,
the measuring system is correctly aligned, and the measuring error
is within the allowance error (tolerance).
Criteria = .DELTA. L W - .DELTA. L K .DELTA. L W .times. 100 = L FW
- L CW - L FK - L CK L FW - L CW .ltoreq. 2 ( % ) ( Equation 6 )
##EQU00014##
[0093] Here, .DELTA.L.sub.W is the absolute difference between the
full white luminance L.sub.FW and the circle white luminance
L.sub.CW, .DELTA.L.sub.K is the absolute difference between the
full black luminance L.sub.FK and the circle black luminance
L.sub.CK, L.sub.FW is the full white luminance, L.sub.FK is the
full black luminance, L.sub.CW is the circle white luminance, and
L.sub.CK is the circle black luminance.
[0094] Using the purity, the new standard for evaluating the
quality of a transparent display, it is possible to have very exact
evaluating values that are proportional to the actual clearness and
luminance of the background scene that would be recognized by the
observer. In more detail, according to the related art, even though
two transparent displays have the same clarity value, the
observer's ability to view the background through these two
transparent displays would be very different due to a small
difference in the haze values. According to embodiments of the
present invention, the purity values would be very different for
these same two transparent displays. In another situation, two
transparent displays of which the clarities are similar to each
other, the observer's recognition of one display having better haze
value may actually be worse than the other display having a worse
haze value. In that situation, according to an embodiment of the
present invention, the purity values would be proportional to the
degree of the observer's recognition.
[0095] That is, it is impossible to obtain an objective and exact
evaluation with the clarity and/or the haze evaluation methods. In
contrast, it is possible to provide an objective and exact
evaluation standard for the quality of a transparent display using
the purity standard.
[0096] Hereinafter, referring to FIG. 8, a method for measuring the
purity according to an embodiment of the present invention will be
explained in detail. FIG. 8 is a flow chart illustrating a method
for measuring the purity, the new standard for evaluating the
quality of a transparent display, according to an embodiment of the
present invention.
[0097] A background BG is placed as representing any one of the
full white pattern FW, the circle white pattern CW, the circle
black pattern CK, and the full black pattern FK is selectively
represented. A light detector LMD is placed at a position spaced
1.5 m away from the background BG (referring to S110).
[0098] By using a properly designed jig for measurement when
installing the background BG and the light detector LMD, it is
possible to align the center of the circle white pattern CW and/or
the circle black pattern CK with the center of the receiving lens
AP of the light detector LMD. When the measuring system is designed
as a portable system, a step may be provided for using a specific
alignment device for aligning the center of the circle white
pattern CW and/or the circle black pattern CK with the center of
the receiving lens AP of the light detector LMD (referring to
S111). In FIG. 8, the step of S111 may be optional and is shown as
a dotted line.
[0099] A transparent display TS is placed between the background BG
and the light detector LMD. Specifically, the transparent display
TS can be located at a position spaced 0.5 m apart from the light
detector LMD (S120). Since the transparent display TS may have a
different size, even though a jig is used to install the
transparent display TS, it may be difficult to align the center of
the transparent display TS exactly with the center of the circle
white pattern CW and/or the circle black pattern CK and to the
center of the receiving lens AP of the light detector LMD.
[0100] When installing the transparent display TS it is preferable
that the alignment is performed correctly. For example, the
alignment process can be performed using the center point of the
transparent display TS. However, it may be more accurate to perform
the alignment process using the center point of the circle
transparent pattern CTP displayed at the center of the transparent
display TS. For example, after the circle transparent pattern CTP
is represented at the center of the transparent display TS, then
the alignment process can be performed using the center point of
the circle transparent pattern CTP by moving the circle transparent
pattern CTP on the transparent display TS. There may be various
methods for conducting the alignment process. One detailed method
will be explained later (referring to S130).
[0101] The circle transparent pattern CTP is displayed at the
center of the transparent display TS. The full white pattern FW,
the circle white pattern CW, the circle black pattern CK and/or the
full black pattern FK are sequentially displayed on the background
BG. Using the light detector LMD, the luminance for each of these
patterns is measured. That is, the measured values are the full
white luminance L.sub.FW, the full black luminance L.sub.FK, the
circle white luminance L.sub.CW and the circle black luminance
L.sub.CK (S140).
[0102] Using the Equations 4 and 5, the purity can be calculated
(S150). Further, using Equation 6, it is evaluated whether the
measurement error of the purity acquired in the step S150 is within
the allowance error or not. When the error evaluation result is
outside of the allowance error, it may mean that the center of the
circle transparent pattern CTP is not properly aligned with the
center of the circle white pattern CW and/or the circle black
pattern CK positioned at the background BG and the center of the
receiving lens AP of the light detector LMD. In that case, the
method returns back to step S130, and the alignment process of the
transparent display TS is repeated until the error evaluating
result is within the allowance error (according to the Equation 6)
(S160). When the error evaluation result obtained at step S160 is
within the allowance error, the purity of the transparent display
TS is decided as the calculated value in step S150 (S170).
[0103] In the explanation of embodiments of the present invention,
the error evaluation step using the Equation 6 is necessarily
included. However, when the measuring system is ensured to be
within the alignment allowance error, this error evaluation step
can be omitted. In the actual manufacturing process of the
transparent displays, the purity is measured at the quality
conformation step. In that situation, a plurality of the
transparent display TS having the same size are repeatedly checked.
In that situation, it is preferable that the allowance error
evaluation process be performed when the periodical inspection is
performed for the manufacturing system.
[0104] Until now, the explanation is based on the condition in
which the patterns disposed at the background BG have the pure full
gray scale level and the luminance corresponds to these scale
levels. That is, the full white pattern has 100% luminance and the
full black pattern has 0% luminance. For the circle white pattern,
the ambient has the full black luminance of 0% and the circle
pattern has 100% luminance. In addition, for the circle black
pattern, the ambient has the full white luminance of 100% and the
circle pattern has 0% luminance.
[0105] In that situation, the background BG should be prepared as a
standardized pattern. When a standardized pattern is not prepared,
the measured purity cannot be decided as an exact value of the
purity. For example, when the size of the background BG satisfying
the standard is 20 inches and the size of the transparent display
TS is larger than 40 inch, it is hard to correctly measure the
purity value. For example, a properly sized standard background BG
should be prepared. Much time may be required for preparing a new
standard background and evaluating whether the background BG
satisfies the standard.
[0106] Therefore, in a preferred embodiment of the present
invention, a method is provided for measuring the purity exactly,
even though the patterns disposed at the background BG do not
satisfy the pure full gray scale levels. The purity measuring
system according to a preferred embodiment of the present invention
has the same structure as the system mentioned above. The
difference being that the white level may not be 100% and/or the
black level may not be 0% when the patterns are disposed at the
background BG.
[0107] In a preferred embodiment of the present invention, after
installing the background BG and the light detector LMD, the
reference luminance L.sub.ref is firstly measured before installing
the transparent display TS. In order to measure the reference
luminance L.sub.ref, without the transparent display TS, the full
white pattern FW, the full black pattern FK, the circle white
pattern CW and the circle black pattern CK are disposed
sequentially. Then, without the transparent display TS, the
luminance of the patterns including the reference full white
luminance L.sub.FW,w/o, the reference full black luminance
L.sub.FK,w/o, the reference circle white luminance L.sub.CW,w/o,
and the reference circle black luminance L.sub.CK,w/o are measured.
In some instances, the reference circle black luminance
L.sub.CK,w/o may not be measured. Here, `w/o` means the condition
in which the transparent display TS is not installed. Then, the
reference purity P.sub.ref can be acquired as the following
Equation 7.
P ref = L CW , w / o - L FK , w / o L FW , w / o - L FK , w / o (
Equation 7 ) ##EQU00015##
[0108] Here, L.sub.FW,w/o is the reference full white luminance,
L.sub.FK,w/o is the reference full black luminance, and
L.sub.CW,w/o is the reference circle white luminance.
[0109] After that, the transparent display TS is installed between
the background BG and the light detector LMD, and the measuring of
the purity P.sub.exp is calculated. As mentioned above, displaying
the full white pattern FW, the full black pattern FK, the circle
white pattern CW and the circle black pattern CK are displayed on
the background BG, the luminance including the full white luminance
L.sub.FW,w/, the full black luminance L.sub.FK,w/, the circle white
luminance L.sub.CW,w/ and the circle black luminance L.sub.CK,w/
are measured, respectively. In some instances, the circle black
luminance L.sub.FK,w/ may be not measured. Here, `w/` means the
condition in which the transparent display TS is installed. Then,
the measured purity P.sub.exp using the background BG can be
acquired as the following Equation 8.
P exp = L CW , w / - L FK , w / L FW , w / - L FK , w / ( Equation
8 ) ##EQU00016##
[0110] Here, L.sub.FW,w/ is the measured full white luminance of
the transparent display TS, L.sub.FK,w/ is the measured full black
luminance of the transparent display TS, and L.sub.CW,w/ is the
measured circle white luminance of the transparent display TS.
[0111] In the above preferred embodiment of the present invention,
unlike the former explained embodiment, the measured purity cannot
be decided as the purity of the transparent display. The reason
being that the measured purity is not acquired by considering the
background. Therefore, with considering the background, it is
possible to decide the correct purity. That is, using the reference
purity P.sub.ref and the measured purity P.sub.exp, the purity can
be acquired using the following Equation 9.
Purity ( % ) = P exp P ref .times. 100 ( Equation 9 )
##EQU00017##
[0112] Here, P.sub.ref is the reference purity without the
transparent display, and P.sub.exp is the measured purity with the
transparent display.
[0113] In a preferred embodiment of the present invention, a method
is provided for measuring the purity when the patterns displayed on
the background BG do not have the pure full gray scale level. For
example, when the background is configured using a flat panel
display such as a liquid crystal display, an organic light emitting
diode display or a plasma display, the gray scale of the patterns
represented on the flat panel display may not be in compliance with
the standard gray scale. In that case, as mentioned in the
preferred embodiment, it is preferable that the purity be decided
by using the reference purity and the measured purity.
[0114] Hereinafter, referring to FIG. 9, we will explain about the
method for measuring the purity according to the preferred
embodiment of the present invention, in detail. FIG. 9 is a flow
chart illustrating a method for measuring the purity the new
standard evaluating the quality of the transparent display,
according to a preferred embodiment of the present invention.
[0115] A background BG is placed for selectively displaying any one
of the full white pattern FW, the circle white pattern CW, the
circle black pattern CK and the full black pattern FK. A light
detector LMD is placed at the position which is 1.5 m away from the
background BG (FIG. 9).
[0116] By using a properly designed jig for measurement when
installing the background BG and the light detector LMD, it is
possible to align the center of the circle white pattern CW and/or
the circle black pattern CK with the center of the receiving lens
AP of the light detector LMD. In the situation that the measuring
system is designed as a portable system, a step may be provided for
aligning the center of the circle white pattern CW and/or the
circle black pattern CK with the center of the receiving lens AP of
the light detector LMD using a specific alignment device (S211). In
FIG. 9, the step of S211 may be optional, thus it is shown as a
dotted line.
[0117] On the background BG, the full white pattern FW, the circle
white pattern CW, the circle black pattern CK, and/or the full
black pattern FK are sequentially displayed. Each luminance of each
pattern is measured using the light detector LMD. That is, the
reference full white luminance L.sub.FW,w/o, the reference full
black luminance L.sub.FK,w/o, the reference circle white luminance
L.sub.CW,w/o, and the reference circle black luminance L.sub.CK,w/o
are measured (S215). Using the Equation 7, the reference purity
P.sub.ref is calculated (S217).
[0118] A transparent display TS is placed between the background BG
and the light detector LMD. Particularly, the transparent display
TS can be located at a position spaced 0.5 m away from the light
detector LIVID (S220). As the transparent display TS may have a
different size, even when using a jig, it may be difficult to align
the center of the transparent display TS exactly with the center of
the circle white pattern CW and/or the circle black pattern CK and
with the center of the receiving lens AP of the light detector
LIVID, just by installing the transparent display TS.
[0119] When installing the transparent display TS it is preferable
that the alignment is performed correctly. For example, the
alignment process can be performed using the center point of the
transparent display TS. However, it may be more accurate to perform
the alignment process using the center point of the circle
transparent pattern CTP displayed at the center of the transparent
display TS. For example, after the circle transparent pattern CTP
is represented at the center of the transparent display TS, then an
alignment process can be performed using the center point of the
circle transparent pattern CTP by moving the circle transparent
pattern CTP on the transparent display TS. There may be various
methods for conducting the alignment process. One detailed method
will be explained later (S230).
[0120] The circle transparent pattern CTP is displayed at the
center of the transparent display TS. The full white pattern FW,
the circle white pattern CW, the circle black pattern CK and/or the
full black pattern FK are sequentially displayed on the background
BG. Using the light detector LIVID, the luminance of each of these
patterns is measured. That is, the measured values are the measured
full white luminance L.sub.FW,w/, the measured full black luminance
L.sub.FK,w/, the measured circle white luminance L.sub.CW,w/ and
the measured circle black luminance L.sub.CK,w/ (referring to
S240).
[0121] Using the Equation 8, the measured purity P.sub.exp may be
calculated (S250). Further, using Equation 6, it is evaluated
whether the measurement error of the purity acquired in the step
S250 is within the allowance error or not. When the error
evaluation result is outside of the allowance error, it may
indicate that the center of the circle transparent pattern CTP is
not aligned with the center of the circle white pattern CW and/or
the circle black pattern CK disposed at the background BG and with
the center of the receiving lens AP of the light detector LMD. In
that situation, the method returns back to the step S230, and the
alignment process of the transparent display TS is repeated until
the error evaluating result is within the allowance error
(according to the Equation 6) (S260).
[0122] When the error evaluation result obtained at the step S260
is within the allowance error, substituting the measured purity
P.sub.exp acquired in the step S250 and the reference purity
P.sub.ref acquired in the step 217 into the Equation 9, the purity
of the transparent display TS is decided (referring to S270).
[0123] Hereinafter, referring to FIG. 10, an alignment method for
ensuring the accuracy of the measurement of the purity according to
an embodiment of the present invention will be explained. FIG. 10
is a perspective view illustrating a system for measuring the
purity according to an embodiment of the present invention. While
FIG. 6 is a schematic diagram illustrating a system for measuring
the purity, FIG. 10 is a diagram illustrating a system for
measuring the purity. The measuring system and the alignment
process are not restricted by this embodiment.
[0124] A background jig BZ for installing a background BG may be
located at a point. A display configured to represent any one of
the full white pattern FW, the circle white pattern CW, the circle
black pattern CK, and the full black pattern FK may be installed at
the background jig BZ. Any one panel or sheet having any one of the
full white pattern FW, the circle white pattern CW, the circle
black pattern CK, and the full black pattern FK may be selectively
installed at the background jig BZ. For example, the background jig
BZ may include a first holding means HM1 for assembling and/or
disassembling the panel or sheet. Further, the background jig BZ
may comprise a first alignment means AM1 for alignment in the
system. For example, the first alignment means AM1 may include a
first align mark MK1 having a `+` shape and/or a first detector DT1
for recognizing the first align mark MK1.
[0125] At a position 1.5 m away from the background jig BZ, a light
detector jig LZ for installing a light detector LIVID can be
placed. The light detector jig LZ may comprise a second holding
means HM2 for installing the light detector LMD and a second
alignment means AM2. The second alignment means AM2 may include a
second detector DT2 for recognizing the first align mark MK1 of the
first alignment means AM1. Otherwise, The second alignment means
AM2 may include a second align mark MK2 which can be recognized by
the first detector DT1 of the alignment means AM1.
[0126] Using the first alignment means AM1 and the second alignment
means AM2 included in the background zig BZ and the light detector
zig LZ, respectively, the center of the background BG can be
aligned with the center of the lens of the light detector LIVID.
After locating the background jig BZ and the light detector jig LZ
at their respective positions, and aligning the first alignment
means AM1 with the second alignment means AM2, the background BG
can be set on the background jig BZ and the light detector LIVID
can be set on the light detector jig LZ. Then, automatically, the
background BG can be aligned with the light detector LMD. That is,
the alignment axis of the system for measuring the purity is
established.
[0127] A transparent display jig TZ is placed between the
background zig BZ and the light detector jig LZ. Especially, the
transparent display jig TZ is located at a position 0.5 m away from
the light detector jig LZ. The transparent display jig TZ may
include a third holding means HM3 for assembling and/or
disassembling a transparent display TS. It is preferable that a
system for measuring the purity according to an embodiment of the
present invention can measure various sizes of the transparent
display TS. Therefore, it is preferable that the third holding
means HM3 of the transparent display jig TZ may be configured to
hold various sizes of the transparent display TS.
[0128] As the size of the transparent display TS is not fixed, the
position of the center point of the transparent display TS is not
fixed. It is possible to set the horizontal position of the center
point of various transparent displays TS on a known point. The
horizontal coordinate of the center point of the transparent
display TS can be set on the horizontal coordinates of the center
point of the background BG or the light detector LMD. Therefore,
the transparent display jig TZ may include a third alignment means
AM3 for aligning the transparent display jig TZ. For example, the
third alignment means AM3 may have a third detector DT3 for
recognizing the first alignment mark MK1 and a fourth detector DT4
for recognizing the second alignment mark MK2. As the vertical
coordinate of the center of the transparent display TS may be
varied, it is preferable that the transparent display jig TZ may
include an adjuster ADJ for controlling the height of the
transparent display TS.
[0129] After installing the transparent display TS on the
transparent display jig TZ, a circle transparent pattern CTP can be
displayed on the center of the transparent display TS. To do so, a
computer COM may be connected to the transparent display TS for
providing the display information corresponding to the circle
transparent pattern CTP. In this instance, the computer COM may
have a program for adjusting the location of the circle transparent
pattern CTP on the transparent display TS. Further, a monitor MON
for confirming the position of the circle transparent pattern CTP
on the transparent display TS may be included. Observing the circle
transparent pattern CTP through the monitor MON, the center
position of the circle transparent pattern CTP can be controlled
and/or adjusted to be aligned onto the center of the transparent
display TS.
[0130] There may be various methods for adjusting the height of the
transparent display TS. For example, a LASER tool can be installed
at the center of the background BG (or the center of the patterns
of the background BG) and then the LASER beam can be radiated to
the transparent display TS. Then, it is possible to check whether
the center of the circle transparent pattern CTP is aligned onto
the center of the background BG (or the alignment axis of the
system). Of course, even though there are many other methods, here
we will not explain.
[0131] Changing the patterns on the background BG and measuring
each luminance, the errors can be calculated by the Equation 6.
When the error is outside of the allowance error range, the
position of the circle transparent pattern CTP should be changed as
to be exactly aligned onto the alignment axis of the system.
[0132] For the situation that the diagonal size of the transparent
display TS is smaller than 10 inches, the purity can be acquired by
measuring on one central portion of the transparent display TS.
However, for the case that the diagonal size of the transparent
display TS is larger than 50 inches, it is required to check and/or
evaluate the purities on various positions over the whole surface
of the transparent display TS that are the same or similar. To do
so, the circle transparent pattern CTP should be moved over the
transparent display TS, and the moved center point of the circle
transparent pattern CTP should be re-aligned onto the alignment
axis of the system. After that the purity is decided again and
again.
[0133] Until now, a measuring system and an alignment process have
been explained with a simple model. However, with an automation
system, it is possible to establish an automatic system for
evaluating and/or measuring the purity more easily, quickly and
exactly.
[0134] While the embodiments of the present invention have been
described in detail with reference to the drawings, it will be
understood by those skilled in the art that the invention can be
implemented in other specific forms without changing the technical
spirit or essential features of the invention. Therefore, it should
be noted that the forgoing embodiments are merely illustrative in
all aspects and are not to be construed as limiting the invention.
The scope of the invention is defined by the appended claims rather
than the detailed description of the invention. All changes or
modifications or their equivalents made within the meanings and
scope of the claims should be construed as falling within the scope
of the invention.
* * * * *